Question about bubbles on goldfish tails?

I have a friend that has some goldfish and their tails has like bubbles on them. I have never heard of this. She called me up on the phone to ask me what to do and told me they look like bubbles on their tails and the tails are turned backwards now. Has anyone runned into this problem? I have goldfish also and never have heard or seen of this. Any help would be thankful so I can tell my friend what to do.